Process for producing grain-oriented electromagnetic steel strip

Abstract

In a process for the production of a grain-oriented electromagnetic steel strip, a slab is heated, hot-rolled, cold-rolled, and subjected to a decarburization annealing and secondary recrystallization annealing steps. Grain coarsening is likely to occur during the high temperature heating and remain in the final product as streaks. The secondary recrystallization is, therefore, incomplete due to the streaks. In order to remove this disadvantage, the work piece is subjected to at least two rolling passes, wherein the high circumferential speed roll of one pair of the rolls and the low circumferential speed roll of another pair of the rolls are arranged on the same side of the work piece.

We claim: 
     
       1. A process for producing a grain-oriented electro-magnetic steel strip or sheet product from a slab of continuously cast steel, comprising hot rolling said slab into a hot-rolled strip by passage through a plurality of roll stands wherein at least two of the roll stands have a rolling temperature within the range of from 1250° to 950° C. and each of said two roll stands has upper and lower working rolls which relative to each other are circumferentially high-speed and low-speed rolls and the upper roll of one roll stand is a high-speed roll and the upper roll of the other of the said two roll stands is a low-speed roll, cold rolling said hot-rolled strip into a cold-rolled strip and recrystallization annealing the cold-rolled strip so as to produce said product. 
     
     
       2. A process according to claim 1 characterized in that said steel slab contains at least one inhibitor component effective in the inhibition of grain growth. 
     
     
       3. A process as recited in claim 1 or 2 characterized in that said continuously cast slab is heated to a temperature of not lower than 1300° C. and then hot rolled. 
     
     
       4. A process according to claim 3 wherein the ratio of the unequal roll-circumferential speeds defined by: ##EQU2## wherein the v i  and V i  are the low and high circumferential speeds of the rollers of a given roll stand (i), is at least 5%.